Coated abrasive products typically include a flexible backing material which is overcoated with an abrasive coating. The abrasive coating commonly includes a first coating, typically called a “make” coating which is first applied to the upper surface of the backing and, while the make coating is still sufficiently uncured, abrasive particles are deposited into the make coating to become partially embedded therein. The make coating is then at least partially cured and the abrasive particles are typically further secured within the coated abrasive product by the addition of a size coating which overlays the make coating and the abrasive particles. Following a full curing of the make and size coatings, a coated abrasive product is produced. A coated abrasive product may also include an abrasive product made by applying to one surface of the backing a blend of abrasive particles in a curable binder. The blend is typically coated by suitable means over the upper surface of the backing and then cured. The surface of the abrasive coating may also be modified prior to curing to include raised portions and depressed portions to give a three-dimensional or structured abrasive surface.
In some instances, it is desirable to actually impart a three-dimensional surface to the backing, instead of imparting it to the abrasive coating itself If the backing is imparted with a three-dimensional surface the resultant surface on which the abrasive coating is applied typically includes depressed portions and raised portions which are commonly flat in the raised areas with the raised areas generally being deployed in the same plane to provide a discontinuous abrasive surface.
Most coated abrasive products are converted into any of a variety of shapes such as rectangular sheets, disc shapes, elongate strips and elongate strips which are fastened on ends to provide an abrasive belt. Abrasive discs are typically utilized in sanding devices such as an orbital sander and thus require on their non-abrasive side some means of attaching the coated abrasive disc the movable pad contained on the sanding device. It is fairly commonplace to put a coating of a pressure sensitive adhesive composition either on the non-abrasive side of the abrasive disc or on the support pad to which it is applied with the surface to which it is to be attached being a surface which is adapted to provide a good adhesive bond between the adhesive coating and the surface. Other mechanical attachment systems are known. For example, the backside of the abrasive article may contain a loop substrate. The purpose of the loop substrate is to provide a means for an abrasive product such as a disc to be securely engaged with hooks on a support pad. Moreover, a sheet which includes erect filament stems which have had their distal ends flattened may also be employed as an engagement device for engagement with a loop substrate. The loop substrate may either be applied to the backside of the abrasive sheet material or to the support to which it will be attached, with the other side being the engaging member, i.e., a sheet which includes a multiplicity of hooks or stems with flattened distal ends.
Prior to the present invention a manufacturer of an abrasive sheet material which included (1) a backing having a raised portions and depressed portions on the surface which is to be coated with an abrasive coating and (2) on the backside of the backing to which one part of a two part mechanical engagement system is to be applied was required to accomplish this result in a multi-step operation. Typically, the backing was first prepared with raised areas and depressed areas. Then the abrasive coating was applied at least to the raised areas. A subsequent operation was required to laminate a sheet material which included one part of a two part mechanical engagement system such as a sheet bearing hooks or the stems with distal ends flattened.